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	$147.95	4.402%	$154.4628	$154.46	$154.45	$154.50
Purchase #2	$52.56	13.217%	$59.5069	$59.51	$59.50	$59.50
Purchase #3	$212.70	9.660%	$233.2468	$233.25	$233.25	$233.20
Purchase #4	$67.28	7.471%	$72.3065	$72.31	$72.30	$72.30
Purchase #5	$242.76	3.680%	$251.6936	$251.69	$251.70	$251.70
Purchase #6	$190.50	4.615%	$199.2916	$199.29	$199.30	$199.30
Purchase #7	$141.89	6.160%	$150.6304	$150.63	$150.65	$150.60
7 purchase totals =	$1,055.64		$1,121.1386	$1,121.14	$1,121.15	$1,121.10