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	$104.82	11.205%	$116.5651	$116.57	$116.55	$116.60
Purchase #2	$158.77	7.739%	$171.0572	$171.06	$171.05	$171.10
Purchase #3	$167.50	10.623%	$185.2935	$185.29	$185.30	$185.30
Purchase #4	$91.26	4.268%	$95.155	$95.16	$95.15	$95.20
Purchase #5	$242.68	6.389%	$258.1848	$258.18	$258.20	$258.20
Purchase #6	$162.27	5.110%	$170.562	$170.56	$170.55	$170.60
Purchase #7	$136.69	7.229%	$146.5713	$146.57	$146.55	$146.60
7 purchase totals =	$1,063.99		$1,143.3889	$1,143.39	$1,143.35	$1,143.60