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	$95.80	6.771%	$102.2866	$102.29	$102.30	$102.30
Purchase #2	$55.38	11.512%	$61.7553	$61.76	$61.75	$61.80
Purchase #3	$179.98	3.323%	$185.9607	$185.96	$185.95	$186.00
Purchase #4	$96.86	6.227%	$102.8915	$102.89	$102.90	$102.90
Purchase #5	$121.40	7.197%	$130.1372	$130.14	$130.15	$130.10
Purchase #6	$142.41	3.566%	$147.4883	$147.49	$147.50	$147.50
Purchase #7	$223.46	6.617%	$238.2463	$238.25	$238.25	$238.20
7 purchase totals =	$915.29		$968.7659	$968.78	$968.80	$968.80