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	$174.28	5.701%	$184.2157	$184.22	$184.20	$184.20
Purchase #2	$59.85	12.583%	$67.3809	$67.38	$67.40	$67.40
Purchase #3	$74.31	10.493%	$82.1073	$82.11	$82.10	$82.10
Purchase #4	$12.96	7.325%	$13.9093	$13.91	$13.90	$13.90
Purchase #5	$233.48	11.514%	$260.3629	$260.36	$260.35	$260.40
Purchase #6	$82.51	13.640%	$93.7644	$93.76	$93.75	$93.80
Purchase #7	$141.28	4.277%	$147.3225	$147.32	$147.30	$147.30
7 purchase totals =	$778.67		$849.0630	$849.06	$849.00	$849.10