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	$123.50	3.390%	$127.6867	$127.69	$127.70	$127.70
Purchase #2	$76.37	7.558%	$82.142	$82.14	$82.15	$82.10
Purchase #3	$60.79	7.575%	$65.3948	$65.39	$65.40	$65.40
Purchase #4	$229.40	4.680%	$240.1359	$240.14	$240.15	$240.10
Purchase #5	$234.83	12.476%	$264.1274	$264.13	$264.15	$264.10
Purchase #6	$249.66	8.258%	$270.2769	$270.28	$270.30	$270.30
Purchase #7	$144.71	3.555%	$149.8544	$149.85	$149.85	$149.90
7 purchase totals =	$1,119.26		$1,199.6181	$1,199.62	$1,199.70	$1,199.60