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	$128.97	10.145%	$142.054	$142.05	$142.05	$142.10
Purchase #2	$102.32	9.234%	$111.7682	$111.77	$111.75	$111.80
Purchase #3	$32.94	6.415%	$35.0531	$35.05	$35.05	$35.10
Purchase #4	$228.33	4.866%	$239.4405	$239.44	$239.45	$239.40
Purchase #5	$210.82	5.144%	$221.6646	$221.66	$221.65	$221.70
Purchase #6	$45.92	13.872%	$52.29	$52.29	$52.30	$52.30
Purchase #7	$30.78	6.189%	$32.685	$32.69	$32.70	$32.70
7 purchase totals =	$780.08		$834.9554	$834.95	$834.95	$835.10