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	$171.93	12.870%	$194.0574	$194.06	$194.05	$194.10
Purchase #2	$223.66	13.396%	$253.6215	$253.62	$253.60	$253.60
Purchase #3	$209.94	3.214%	$216.6875	$216.69	$216.70	$216.70
Purchase #4	$42.46	6.538%	$45.236	$45.24	$45.25	$45.20
Purchase #5	$80.71	10.106%	$88.8666	$88.87	$88.85	$88.90
Purchase #6	$149.74	10.339%	$165.2216	$165.22	$165.20	$165.20
Purchase #7	$89.84	7.864%	$96.905	$96.91	$96.90	$96.90
7 purchase totals =	$968.28		$1,060.5956	$1,060.61	$1,060.55	$1,060.60