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	$235.46	10.220%	$259.524	$259.52	$259.50	$259.50
Purchase #2	$64.30	10.753%	$71.2142	$71.21	$71.20	$71.20
Purchase #3	$115.34	7.299%	$123.7587	$123.76	$123.75	$123.80
Purchase #4	$100.81	8.865%	$109.7468	$109.75	$109.75	$109.70
Purchase #5	$63.67	13.625%	$72.345	$72.35	$72.35	$72.30
Purchase #6	$224.50	9.278%	$245.3291	$245.33	$245.35	$245.30
Purchase #7	$195.37	8.579%	$212.1308	$212.13	$212.15	$212.10
7 purchase totals =	$999.45		$1,094.0486	$1,094.05	$1,094.05	$1,093.90