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	$145.82	4.193%	$151.9342	$151.93	$151.95	$151.90
Purchase #2	$205.25	8.781%	$223.273	$223.27	$223.25	$223.30
Purchase #3	$238.55	13.384%	$270.4775	$270.48	$270.50	$270.50
Purchase #4	$59.76	12.287%	$67.1027	$67.10	$67.10	$67.10
Purchase #5	$195.30	6.433%	$207.8636	$207.86	$207.85	$207.90
Purchase #6	$236.67	5.800%	$250.3969	$250.40	$250.40	$250.40
Purchase #7	$26.34	9.857%	$28.9363	$28.94	$28.95	$28.90
7 purchase totals =	$1,107.69		$1,199.9842	$1,199.98	$1,200.00	$1,200.00