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	$218.50	6.811%	$233.382	$233.38	$233.40	$233.40
Purchase #2	$130.43	9.549%	$142.8848	$142.88	$142.90	$142.90
Purchase #3	$227.53	7.355%	$244.2648	$244.26	$244.25	$244.30
Purchase #4	$91.74	7.399%	$98.5278	$98.53	$98.55	$98.50
Purchase #5	$70.74	10.753%	$78.3467	$78.35	$78.35	$78.30
Purchase #6	$69.84	4.361%	$72.8857	$72.89	$72.90	$72.90
Purchase #7	$175.27	13.138%	$198.297	$198.30	$198.30	$198.30
7 purchase totals =	$984.05		$1,068.5888	$1,068.59	$1,068.65	$1,068.60