Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$245.58	3.655%	$254.5559	$254.56	$254.55	$254.60
Purchase #2	$223.93	6.103%	$237.5964	$237.60	$237.60	$237.60
Purchase #3	$211.43	13.870%	$240.7553	$240.76	$240.75	$240.80
Purchase #4	$134.40	6.310%	$142.8806	$142.88	$142.90	$142.90
Purchase #5	$83.73	12.560%	$94.2465	$94.25	$94.25	$94.20
Purchase #6	$164.50	13.261%	$186.3143	$186.31	$186.30	$186.30
Purchase #7	$200.50	12.280%	$225.1214	$225.12	$225.10	$225.10
7 purchase totals =	$1,264.07		$1,381.4704	$1,381.48	$1,381.45	$1,381.50