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	$67.75	5.536%	$71.5006	$71.50	$71.50	$71.50
Purchase #2	$148.28	8.801%	$161.3301	$161.33	$161.35	$161.30
Purchase #3	$243.32	10.507%	$268.8856	$268.89	$268.90	$268.90
Purchase #4	$207.91	6.799%	$222.0458	$222.05	$222.05	$222.00
Purchase #5	$27.59	6.776%	$29.4595	$29.46	$29.45	$29.50
Purchase #6	$209.31	4.541%	$218.8148	$218.81	$218.80	$218.80
Purchase #7	$173.43	4.790%	$181.7373	$181.74	$181.75	$181.70
7 purchase totals =	$1,077.59		$1,153.7737	$1,153.78	$1,153.80	$1,153.70