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	$47.79	12.227%	$53.6333	$53.63	$53.65	$53.60
Purchase #2	$214.30	11.426%	$238.7859	$238.79	$238.80	$238.80
Purchase #3	$36.99	13.729%	$42.0684	$42.07	$42.05	$42.10
Purchase #4	$172.72	10.657%	$191.1268	$191.13	$191.15	$191.10
Purchase #5	$185.94	5.557%	$196.2727	$196.27	$196.25	$196.30
Purchase #6	$171.53	9.752%	$188.2576	$188.26	$188.25	$188.30
Purchase #7	$98.54	9.567%	$107.9673	$107.97	$107.95	$108.00
7 purchase totals =	$927.81		$1,018.1120	$1,018.12	$1,018.10	$1,018.20