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	$165.53	7.711%	$178.294	$178.29	$178.30	$178.30
Purchase #2	$125.35	6.393%	$133.3636	$133.36	$133.35	$133.40
Purchase #3	$76.53	3.723%	$79.3792	$79.38	$79.40	$79.40
Purchase #4	$79.36	12.520%	$89.2959	$89.30	$89.30	$89.30
Purchase #5	$245.41	12.812%	$276.8519	$276.85	$276.85	$276.90
Purchase #6	$39.90	6.525%	$42.5035	$42.50	$42.50	$42.50
Purchase #7	$220.77	11.344%	$245.8141	$245.81	$245.80	$245.80
7 purchase totals =	$952.85		$1,045.5022	$1,045.49	$1,045.50	$1,045.60