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	$88.27	4.649%	$92.3737	$92.37	$92.35	$92.40
Purchase #2	$235.31	5.539%	$248.3438	$248.34	$248.35	$248.30
Purchase #3	$127.88	13.433%	$145.0581	$145.06	$145.05	$145.10
Purchase #4	$106.46	7.353%	$114.288	$114.29	$114.30	$114.30
Purchase #5	$113.67	6.854%	$121.4609	$121.46	$121.45	$121.50
Purchase #6	$114.71	11.298%	$127.6699	$127.67	$127.65	$127.70
Purchase #7	$93.38	6.418%	$99.3731	$99.37	$99.35	$99.40
7 purchase totals =	$879.68		$948.5675	$948.56	$948.50	$948.70