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	$147.28	11.800%	$164.659	$164.66	$164.65	$164.70
Purchase #2	$69.32	6.717%	$73.9762	$73.98	$74.00	$74.00
Purchase #3	$247.50	7.221%	$265.372	$265.37	$265.35	$265.40
Purchase #4	$196.72	4.624%	$205.8163	$205.82	$205.80	$205.80
Purchase #5	$11.38	12.585%	$12.8122	$12.81	$12.80	$12.80
Purchase #6	$85.64	13.112%	$96.8691	$96.87	$96.85	$96.90
Purchase #7	$242.27	12.427%	$272.3769	$272.38	$272.40	$272.40
7 purchase totals =	$1,000.11		$1,091.8817	$1,091.89	$1,091.85	$1,092.00