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	$146.62	6.123%	$155.5975	$155.60	$155.60	$155.60
Purchase #2	$70.31	3.604%	$72.844	$72.84	$72.85	$72.80
Purchase #3	$237.76	4.512%	$248.4877	$248.49	$248.50	$248.50
Purchase #4	$36.67	13.590%	$41.6535	$41.65	$41.65	$41.70
Purchase #5	$54.60	9.343%	$59.7013	$59.70	$59.70	$59.70
Purchase #6	$209.99	5.817%	$222.2051	$222.21	$222.20	$222.20
Purchase #7	$167.49	9.454%	$183.3245	$183.32	$183.30	$183.30
7 purchase totals =	$923.44		$983.8136	$983.81	$983.80	$983.80