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	$152.39	9.360%	$166.6537	$166.65	$166.65	$166.70
Purchase #2	$51.51	8.314%	$55.7925	$55.79	$55.80	$55.80
Purchase #3	$209.85	6.479%	$223.4462	$223.45	$223.45	$223.40
Purchase #4	$244.44	4.484%	$255.4007	$255.40	$255.40	$255.40
Purchase #5	$69.43	12.588%	$78.1698	$78.17	$78.15	$78.20
Purchase #6	$239.82	9.712%	$263.1113	$263.11	$263.10	$263.10
Purchase #7	$50.69	3.249%	$52.3369	$52.34	$52.35	$52.30
7 purchase totals =	$1,018.13		$1,094.9111	$1,094.91	$1,094.90	$1,094.90