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	$225.62	3.342%	$233.1602	$233.16	$233.15	$233.20
Purchase #2	$65.28	6.664%	$69.6303	$69.63	$69.65	$69.60
Purchase #3	$181.30	10.464%	$200.2712	$200.27	$200.25	$200.30
Purchase #4	$92.96	6.626%	$99.1195	$99.12	$99.10	$99.10
Purchase #5	$59.62	5.538%	$62.9218	$62.92	$62.90	$62.90
Purchase #6	$187.67	5.747%	$198.4554	$198.46	$198.45	$198.50
Purchase #7	$79.25	13.266%	$89.7633	$89.76	$89.75	$89.80
7 purchase totals =	$891.70		$953.3217	$953.32	$953.25	$953.40