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	$225.27	10.230%	$248.3151	$248.32	$248.30	$248.30
Purchase #2	$54.93	11.117%	$61.0366	$61.04	$61.05	$61.00
Purchase #3	$125.59	4.579%	$131.3408	$131.34	$131.35	$131.30
Purchase #4	$103.95	7.142%	$111.3741	$111.37	$111.35	$111.40
Purchase #5	$59.72	9.253%	$65.2459	$65.25	$65.25	$65.20
Purchase #6	$111.37	12.254%	$125.0173	$125.02	$125.00	$125.00
Purchase #7	$243.75	10.123%	$268.4248	$268.42	$268.40	$268.40
7 purchase totals =	$924.58		$1,010.7546	$1,010.76	$1,010.70	$1,010.60