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	$129.69	9.871%	$142.4917	$142.49	$142.50	$142.50
Purchase #2	$110.45	3.872%	$114.7266	$114.73	$114.75	$114.70
Purchase #3	$205.70	8.443%	$223.0673	$223.07	$223.05	$223.10
Purchase #4	$123.59	5.316%	$130.16	$130.16	$130.15	$130.20
Purchase #5	$205.88	10.412%	$227.3162	$227.32	$227.30	$227.30
Purchase #6	$60.50	10.771%	$67.0165	$67.02	$67.00	$67.00
Purchase #7	$213.82	11.434%	$238.2682	$238.27	$238.25	$238.30
7 purchase totals =	$1,049.63		$1,143.0465	$1,143.06	$1,143.00	$1,143.10