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	$175.89	5.352%	$185.3036	$185.30	$185.30	$185.30
Purchase #2	$55.56	10.534%	$61.4127	$61.41	$61.40	$61.40
Purchase #3	$78.49	5.196%	$82.5683	$82.57	$82.55	$82.60
Purchase #4	$140.96	3.308%	$145.623	$145.62	$145.60	$145.60
Purchase #5	$247.89	10.154%	$273.0608	$273.06	$273.05	$273.10
Purchase #6	$203.36	8.725%	$221.1032	$221.10	$221.10	$221.10
Purchase #7	$124.94	9.464%	$136.7643	$136.76	$136.75	$136.80
7 purchase totals =	$1,027.09		$1,105.8359	$1,105.82	$1,105.75	$1,105.90