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	$241.71	8.836%	$263.0675	$263.07	$263.05	$263.10
Purchase #2	$154.98	9.216%	$169.263	$169.26	$169.25	$169.30
Purchase #3	$166.73	5.298%	$175.5634	$175.56	$175.55	$175.60
Purchase #4	$77.88	9.739%	$85.4647	$85.46	$85.45	$85.50
Purchase #5	$131.81	10.410%	$145.5314	$145.53	$145.55	$145.50
Purchase #6	$233.49	3.167%	$240.8846	$240.88	$240.90	$240.90
Purchase #7	$57.77	7.852%	$62.3061	$62.31	$62.30	$62.30
7 purchase totals =	$1,064.37		$1,142.0807	$1,142.07	$1,142.05	$1,142.20