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	$246.25	10.402%	$271.8649	$271.86	$271.85	$271.90
Purchase #2	$90.68	9.465%	$99.2629	$99.26	$99.25	$99.30
Purchase #3	$186.99	9.695%	$205.1187	$205.12	$205.10	$205.10
Purchase #4	$83.72	9.121%	$91.3561	$91.36	$91.35	$91.40
Purchase #5	$194.50	12.448%	$218.7114	$218.71	$218.70	$218.70
Purchase #6	$126.76	11.440%	$141.2613	$141.26	$141.25	$141.30
Purchase #7	$73.47	6.853%	$78.5049	$78.50	$78.50	$78.50
7 purchase totals =	$1,002.37		$1,106.0802	$1,106.07	$1,106.00	$1,106.20