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	$59.36	3.413%	$61.386	$61.39	$61.40	$61.40
Purchase #2	$163.59	4.210%	$170.4771	$170.48	$170.50	$170.50
Purchase #3	$45.32	5.761%	$47.9309	$47.93	$47.95	$47.90
Purchase #4	$200.30	13.661%	$227.663	$227.66	$227.65	$227.70
Purchase #5	$202.36	5.409%	$213.3057	$213.31	$213.30	$213.30
Purchase #6	$79.30	12.251%	$89.015	$89.02	$89.00	$89.00
Purchase #7	$41.89	7.708%	$45.1189	$45.12	$45.10	$45.10
7 purchase totals =	$792.12		$854.8966	$854.91	$854.90	$854.90