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	$175.79	8.811%	$191.2789	$191.28	$191.30	$191.30
Purchase #2	$41.56	6.658%	$44.3271	$44.33	$44.35	$44.30
Purchase #3	$56.40	5.285%	$59.3807	$59.38	$59.40	$59.40
Purchase #4	$149.49	4.242%	$155.8314	$155.83	$155.85	$155.80
Purchase #5	$106.71	5.225%	$112.2856	$112.29	$112.30	$112.30
Purchase #6	$31.63	11.679%	$35.3241	$35.32	$35.30	$35.30
Purchase #7	$83.82	6.446%	$89.223	$89.22	$89.20	$89.20
7 purchase totals =	$645.40		$687.6508	$687.65	$687.70	$687.60