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	$190.30	5.574%	$200.9073	$200.91	$200.90	$200.90
Purchase #2	$174.89	13.711%	$198.8692	$198.87	$198.85	$198.90
Purchase #3	$27.98	6.531%	$29.8074	$29.81	$29.80	$29.80
Purchase #4	$161.72	5.672%	$170.8928	$170.89	$170.90	$170.90
Purchase #5	$189.46	10.385%	$209.1354	$209.14	$209.15	$209.10
Purchase #6	$52.99	12.328%	$59.5226	$59.52	$59.50	$59.50
Purchase #7	$153.27	3.230%	$158.2206	$158.22	$158.20	$158.20
7 purchase totals =	$950.61		$1,027.3553	$1,027.36	$1,027.30	$1,027.30