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	$95.96	7.465%	$103.1234	$103.12	$103.10	$103.10
Purchase #2	$64.26	4.689%	$67.2732	$67.27	$67.25	$67.30
Purchase #3	$149.42	4.798%	$156.5892	$156.59	$156.60	$156.60
Purchase #4	$191.43	6.417%	$203.7141	$203.71	$203.70	$203.70
Purchase #5	$79.95	10.355%	$88.2288	$88.23	$88.25	$88.20
Purchase #6	$77.71	4.498%	$81.2054	$81.21	$81.20	$81.20
Purchase #7	$176.44	13.745%	$200.6917	$200.69	$200.70	$200.70
7 purchase totals =	$835.17		$900.8258	$900.82	$900.80	$900.80