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	$202.29	8.572%	$219.6303	$219.63	$219.65	$219.60
Purchase #2	$80.66	11.238%	$89.7246	$89.72	$89.70	$89.70
Purchase #3	$165.96	10.281%	$183.0223	$183.02	$183.00	$183.00
Purchase #4	$211.75	11.382%	$235.8514	$235.85	$235.85	$235.90
Purchase #5	$123.89	7.450%	$133.1198	$133.12	$133.10	$133.10
Purchase #6	$233.39	13.339%	$264.5219	$264.52	$264.50	$264.50
Purchase #7	$14.88	4.422%	$15.538	$15.54	$15.55	$15.50
7 purchase totals =	$1,032.82		$1,141.4083	$1,141.40	$1,141.35	$1,141.30