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	$92.51	4.358%	$96.5416	$96.54	$96.55	$96.50
Purchase #2	$17.36	8.389%	$18.8163	$18.82	$18.80	$18.80
Purchase #3	$181.49	8.143%	$196.2687	$196.27	$196.25	$196.30
Purchase #4	$113.86	11.704%	$127.1862	$127.19	$127.20	$127.20
Purchase #5	$214.68	4.261%	$223.8275	$223.83	$223.85	$223.80
Purchase #6	$91.55	8.618%	$99.4398	$99.44	$99.45	$99.40
Purchase #7	$191.65	3.418%	$198.2006	$198.20	$198.20	$198.20
7 purchase totals =	$903.10		$960.2807	$960.29	$960.30	$960.20