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	$247.48	6.717%	$264.1032	$264.10	$264.10	$264.10
Purchase #2	$198.36	6.518%	$211.2891	$211.29	$211.30	$211.30
Purchase #3	$105.75	6.750%	$112.8881	$112.89	$112.90	$112.90
Purchase #4	$240.94	11.751%	$269.2529	$269.25	$269.25	$269.30
Purchase #5	$109.33	8.550%	$118.6777	$118.68	$118.70	$118.70
Purchase #6	$9.85	8.810%	$10.7178	$10.72	$10.70	$10.70
Purchase #7	$89.58	9.830%	$98.3857	$98.39	$98.40	$98.40
7 purchase totals =	$1,001.29		$1,085.3145	$1,085.32	$1,085.35	$1,085.40