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	$179.32	10.497%	$198.1432	$198.14	$198.15	$198.10
Purchase #2	$126.47	4.245%	$131.8387	$131.84	$131.85	$131.80
Purchase #3	$64.67	12.515%	$72.7635	$72.76	$72.75	$72.80
Purchase #4	$48.91	13.290%	$55.4101	$55.41	$55.40	$55.40
Purchase #5	$89.85	7.871%	$96.9221	$96.92	$96.90	$96.90
Purchase #6	$225.96	7.559%	$243.0403	$243.04	$243.05	$243.00
Purchase #7	$207.34	11.870%	$231.9513	$231.95	$231.95	$232.00
7 purchase totals =	$942.52		$1,030.0692	$1,030.06	$1,030.05	$1,030.00