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	$104.90	5.253%	$110.4104	$110.41	$110.40	$110.40
Purchase #2	$137.46	7.657%	$147.9853	$147.99	$148.00	$148.00
Purchase #3	$226.50	10.791%	$250.9416	$250.94	$250.95	$250.90
Purchase #4	$250.31	8.113%	$270.6177	$270.62	$270.60	$270.60
Purchase #5	$59.82	3.614%	$61.9819	$61.98	$62.00	$62.00
Purchase #6	$231.54	6.208%	$245.914	$245.91	$245.90	$245.90
Purchase #7	$98.47	13.242%	$111.5094	$111.51	$111.50	$111.50
7 purchase totals =	$1,109.00		$1,199.3603	$1,199.36	$1,199.35	$1,199.30