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	$43.77	3.468%	$45.2879	$45.29	$45.30	$45.30
Purchase #2	$88.65	10.670%	$98.109	$98.11	$98.10	$98.10
Purchase #3	$115.38	10.305%	$127.2699	$127.27	$127.25	$127.30
Purchase #4	$148.40	6.628%	$158.236	$158.24	$158.25	$158.20
Purchase #5	$103.85	7.250%	$111.3791	$111.38	$111.40	$111.40
Purchase #6	$167.84	10.586%	$185.6075	$185.61	$185.60	$185.60
Purchase #7	$210.60	5.756%	$222.7221	$222.72	$222.70	$222.70
7 purchase totals =	$878.49		$948.6115	$948.62	$948.60	$948.60