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	$34.31	10.540%	$37.9263	$37.93	$37.95	$37.90
Purchase #2	$58.84	6.175%	$62.4734	$62.47	$62.45	$62.50
Purchase #3	$25.83	10.758%	$28.6088	$28.61	$28.60	$28.60
Purchase #4	$145.73	4.751%	$152.6536	$152.65	$152.65	$152.70
Purchase #5	$221.41	7.528%	$238.0777	$238.08	$238.10	$238.10
Purchase #6	$130.65	11.370%	$145.5049	$145.50	$145.50	$145.50
Purchase #7	$159.61	13.473%	$181.1143	$181.11	$181.10	$181.10
7 purchase totals =	$776.38		$846.3590	$846.35	$846.35	$846.40