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	$40.78	5.792%	$43.142	$43.14	$43.15	$43.10
Purchase #2	$85.43	13.829%	$97.2441	$97.24	$97.25	$97.20
Purchase #3	$105.35	5.420%	$111.06	$111.06	$111.05	$111.10
Purchase #4	$209.36	5.436%	$220.7408	$220.74	$220.75	$220.70
Purchase #5	$249.57	5.495%	$263.2839	$263.28	$263.30	$263.30
Purchase #6	$229.48	6.318%	$243.9785	$243.98	$244.00	$244.00
Purchase #7	$150.77	7.485%	$162.0551	$162.06	$162.05	$162.10
7 purchase totals =	$1,070.74		$1,141.5044	$1,141.50	$1,141.55	$1,141.50