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	$92.61	11.240%	$103.0194	$103.02	$103.00	$103.00
Purchase #2	$174.71	3.431%	$180.7043	$180.70	$180.70	$180.70
Purchase #3	$62.76	4.265%	$65.4367	$65.44	$65.45	$65.40
Purchase #4	$223.80	6.386%	$238.0919	$238.09	$238.10	$238.10
Purchase #5	$168.78	10.171%	$185.9466	$185.95	$185.95	$185.90
Purchase #6	$46.72	10.110%	$51.4434	$51.44	$51.45	$51.40
Purchase #7	$239.97	11.853%	$268.4136	$268.41	$268.40	$268.40
7 purchase totals =	$1,009.35		$1,093.0559	$1,093.05	$1,093.05	$1,092.90