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	$147.37	8.490%	$159.8817	$159.88	$159.90	$159.90
Purchase #2	$12.42	9.390%	$13.5862	$13.59	$13.60	$13.60
Purchase #3	$128.78	5.819%	$136.2737	$136.27	$136.25	$136.30
Purchase #4	$30.76	8.442%	$33.3568	$33.36	$33.35	$33.40
Purchase #5	$236.98	7.660%	$255.1327	$255.13	$255.15	$255.10
Purchase #6	$159.70	7.196%	$171.192	$171.19	$171.20	$171.20
Purchase #7	$226.85	6.166%	$240.8376	$240.84	$240.85	$240.80
7 purchase totals =	$942.86		$1,010.2607	$1,010.26	$1,010.30	$1,010.30