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	$38.86	5.843%	$41.1306	$41.13	$41.15	$41.10
Purchase #2	$85.36	3.784%	$88.59	$88.59	$88.60	$88.60
Purchase #3	$56.48	9.213%	$61.6835	$61.68	$61.70	$61.70
Purchase #4	$46.93	3.471%	$48.5589	$48.56	$48.55	$48.60
Purchase #5	$41.36	4.157%	$43.0793	$43.08	$43.10	$43.10
Purchase #6	$170.85	4.417%	$178.3964	$178.40	$178.40	$178.40
Purchase #7	$152.29	8.814%	$165.7128	$165.71	$165.70	$165.70
7 purchase totals =	$592.13		$627.1515	$627.15	$627.20	$627.20