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	$59.65	12.771%	$67.2679	$67.27	$67.25	$67.30
Purchase #2	$229.37	9.650%	$251.5042	$251.50	$251.50	$251.50
Purchase #3	$52.76	12.253%	$59.2247	$59.22	$59.20	$59.20
Purchase #4	$145.64	5.867%	$154.1847	$154.18	$154.20	$154.20
Purchase #5	$5.32	9.629%	$5.8323	$5.83	$5.85	$5.80
Purchase #6	$147.41	5.226%	$155.1136	$155.11	$155.10	$155.10
Purchase #7	$64.61	4.183%	$67.3126	$67.31	$67.30	$67.30
7 purchase totals =	$704.76		$760.4400	$760.42	$760.40	$760.40