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	$68.99	4.869%	$72.3491	$72.35	$72.35	$72.30
Purchase #2	$198.86	6.807%	$212.3964	$212.40	$212.40	$212.40
Purchase #3	$243.71	9.812%	$267.6228	$267.62	$267.60	$267.60
Purchase #4	$115.56	6.468%	$123.0344	$123.03	$123.05	$123.00
Purchase #5	$46.83	8.379%	$50.7539	$50.75	$50.75	$50.80
Purchase #6	$79.55	13.478%	$90.2717	$90.27	$90.25	$90.30
Purchase #7	$170.67	12.709%	$192.3605	$192.36	$192.35	$192.40
7 purchase totals =	$924.17		$1,008.7888	$1,008.78	$1,008.75	$1,008.80