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	$155.34	10.543%	$171.7175	$171.72	$171.70	$171.70
Purchase #2	$228.38	4.385%	$238.3945	$238.39	$238.40	$238.40
Purchase #3	$175.82	7.532%	$189.0628	$189.06	$189.05	$189.10
Purchase #4	$85.57	13.776%	$97.3581	$97.36	$97.35	$97.40
Purchase #5	$96.88	9.575%	$106.1563	$106.16	$106.15	$106.20
Purchase #6	$193.70	3.431%	$200.3458	$200.35	$200.35	$200.30
Purchase #7	$99.71	7.166%	$106.8552	$106.86	$106.85	$106.90
7 purchase totals =	$1,035.40		$1,109.8902	$1,109.90	$1,109.85	$1,110.00