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	$108.87	5.149%	$114.4757	$114.48	$114.50	$114.50
Purchase #2	$225.51	6.222%	$239.5412	$239.54	$239.55	$239.50
Purchase #3	$43.54	7.115%	$46.6379	$46.64	$46.65	$46.60
Purchase #4	$82.77	7.545%	$89.015	$89.02	$89.00	$89.00
Purchase #5	$68.96	12.583%	$77.6372	$77.64	$77.65	$77.60
Purchase #6	$88.33	3.206%	$91.1619	$91.16	$91.15	$91.20
Purchase #7	$227.59	7.170%	$243.9082	$243.91	$243.90	$243.90
7 purchase totals =	$845.57		$902.3771	$902.39	$902.40	$902.30