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	$173.98	5.395%	$183.3662	$183.37	$183.35	$183.40
Purchase #2	$96.45	6.841%	$103.0481	$103.05	$103.05	$103.00
Purchase #3	$183.67	11.535%	$204.8563	$204.86	$204.85	$204.90
Purchase #4	$99.44	12.110%	$111.4822	$111.48	$111.50	$111.50
Purchase #5	$69.29	8.722%	$75.3335	$75.33	$75.35	$75.30
Purchase #6	$44.40	4.804%	$46.533	$46.53	$46.55	$46.50
Purchase #7	$81.54	9.507%	$89.292	$89.29	$89.30	$89.30
7 purchase totals =	$748.77		$813.9113	$813.91	$813.95	$813.90