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	$101.91	9.190%	$111.2755	$111.28	$111.30	$111.30
Purchase #2	$76.71	3.722%	$79.5651	$79.57	$79.55	$79.60
Purchase #3	$41.78	3.636%	$43.2991	$43.30	$43.30	$43.30
Purchase #4	$243.47	8.623%	$264.4644	$264.46	$264.45	$264.50
Purchase #5	$69.71	3.778%	$72.3436	$72.34	$72.35	$72.30
Purchase #6	$129.51	9.672%	$142.0362	$142.04	$142.05	$142.00
Purchase #7	$30.64	6.535%	$32.6423	$32.64	$32.65	$32.60
7 purchase totals =	$693.73		$745.6262	$745.63	$745.65	$745.60