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	$99.57	11.669%	$111.1888	$111.19	$111.20	$111.20
Purchase #2	$138.42	13.345%	$156.8921	$156.89	$156.90	$156.90
Purchase #3	$54.87	9.527%	$60.0975	$60.10	$60.10	$60.10
Purchase #4	$222.51	4.861%	$233.3262	$233.33	$233.35	$233.30
Purchase #5	$25.43	6.386%	$27.054	$27.05	$27.05	$27.10
Purchase #6	$186.81	13.582%	$212.1825	$212.18	$212.20	$212.20
Purchase #7	$245.52	7.409%	$263.7106	$263.71	$263.70	$263.70
7 purchase totals =	$973.13		$1,064.4517	$1,064.45	$1,064.50	$1,064.50