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	$99.91	3.489%	$103.3959	$103.40	$103.40	$103.40
Purchase #2	$53.70	3.491%	$55.5747	$55.57	$55.55	$55.60
Purchase #3	$195.28	7.688%	$210.2931	$210.29	$210.30	$210.30
Purchase #4	$199.59	5.289%	$210.1463	$210.15	$210.15	$210.10
Purchase #5	$209.46	11.142%	$232.798	$232.80	$232.80	$232.80
Purchase #6	$46.76	10.194%	$51.5267	$51.53	$51.55	$51.50
Purchase #7	$171.76	10.824%	$190.3513	$190.35	$190.35	$190.40
7 purchase totals =	$976.46		$1,054.0860	$1,054.09	$1,054.10	$1,054.10