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	$173.35	6.371%	$184.3941	$184.39	$184.40	$184.40
Purchase #2	$155.58	6.497%	$165.688	$165.69	$165.70	$165.70
Purchase #3	$63.31	9.799%	$69.5137	$69.51	$69.50	$69.50
Purchase #4	$232.44	7.606%	$250.1194	$250.12	$250.10	$250.10
Purchase #5	$54.48	9.751%	$59.7923	$59.79	$59.80	$59.80
Purchase #6	$91.30	3.482%	$94.4791	$94.48	$94.50	$94.50
Purchase #7	$222.98	9.225%	$243.5499	$243.55	$243.55	$243.50
7 purchase totals =	$993.44		$1,067.5365	$1,067.53	$1,067.55	$1,067.50