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	$111.74	11.260%	$124.3219	$124.32	$124.30	$124.30
Purchase #2	$98.45	5.864%	$104.2231	$104.22	$104.20	$104.20
Purchase #3	$105.98	10.574%	$117.1863	$117.19	$117.20	$117.20
Purchase #4	$207.69	7.779%	$223.8462	$223.85	$223.85	$223.80
Purchase #5	$135.41	12.488%	$152.32	$152.32	$152.30	$152.30
Purchase #6	$157.97	11.478%	$176.1018	$176.10	$176.10	$176.10
Purchase #7	$106.38	3.314%	$109.9054	$109.91	$109.90	$109.90
7 purchase totals =	$923.62		$1,007.9047	$1,007.91	$1,007.85	$1,007.80