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	$135.46	9.713%	$148.6172	$148.62	$148.60	$148.60
Purchase #2	$216.75	5.856%	$229.4429	$229.44	$229.45	$229.40
Purchase #3	$179.40	8.495%	$194.64	$194.64	$194.65	$194.60
Purchase #4	$67.60	4.478%	$70.6271	$70.63	$70.65	$70.60
Purchase #5	$205.36	13.778%	$233.6545	$233.65	$233.65	$233.70
Purchase #6	$64.90	9.696%	$71.1927	$71.19	$71.20	$71.20
Purchase #7	$63.71	13.453%	$72.2809	$72.28	$72.30	$72.30
7 purchase totals =	$933.18		$1,020.4553	$1,020.45	$1,020.50	$1,020.40