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	$94.74	4.773%	$99.2619	$99.26	$99.25	$99.30
Purchase #2	$97.82	9.855%	$107.4602	$107.46	$107.45	$107.50
Purchase #3	$85.66	4.413%	$89.4402	$89.44	$89.45	$89.40
Purchase #4	$118.70	5.214%	$124.889	$124.89	$124.90	$124.90
Purchase #5	$127.74	10.816%	$141.5564	$141.56	$141.55	$141.60
Purchase #6	$85.92	5.211%	$90.3973	$90.40	$90.40	$90.40
Purchase #7	$86.28	10.685%	$95.499	$95.50	$95.50	$95.50
7 purchase totals =	$696.86		$748.5040	$748.51	$748.50	$748.60