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	$157.66	13.635%	$179.1569	$179.16	$179.15	$179.20
Purchase #2	$242.33	4.872%	$254.1363	$254.14	$254.15	$254.10
Purchase #3	$90.87	10.504%	$100.415	$100.42	$100.40	$100.40
Purchase #4	$177.61	6.362%	$188.9095	$188.91	$188.90	$188.90
Purchase #5	$134.96	11.781%	$150.8596	$150.86	$150.85	$150.90
Purchase #6	$179.72	4.641%	$188.0608	$188.06	$188.05	$188.10
Purchase #7	$36.26	11.463%	$40.4165	$40.42	$40.40	$40.40
7 purchase totals =	$1,019.41		$1,101.9546	$1,101.97	$1,101.90	$1,102.00