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	$84.90	12.359%	$95.3928	$95.39	$95.40	$95.40
Purchase #2	$46.87	5.600%	$49.4947	$49.49	$49.50	$49.50
Purchase #3	$188.74	5.142%	$198.445	$198.45	$198.45	$198.40
Purchase #4	$147.29	6.173%	$156.3822	$156.38	$156.40	$156.40
Purchase #5	$129.50	12.327%	$145.4635	$145.46	$145.45	$145.50
Purchase #6	$91.33	3.345%	$94.385	$94.39	$94.40	$94.40
Purchase #7	$54.54	5.426%	$57.4993	$57.50	$57.50	$57.50
7 purchase totals =	$743.17		$797.0625	$797.06	$797.10	$797.10