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	$186.38	8.202%	$201.6669	$201.67	$201.65	$201.70
Purchase #2	$171.65	7.810%	$185.0559	$185.06	$185.05	$185.10
Purchase #3	$52.40	9.573%	$57.4163	$57.42	$57.40	$57.40
Purchase #4	$102.69	6.252%	$109.1102	$109.11	$109.10	$109.10
Purchase #5	$222.63	9.215%	$243.1454	$243.15	$243.15	$243.10
Purchase #6	$54.82	12.873%	$61.877	$61.88	$61.90	$61.90
Purchase #7	$125.57	13.730%	$142.8108	$142.81	$142.80	$142.80
7 purchase totals =	$916.14		$1,001.0825	$1,001.10	$1,001.05	$1,001.10