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	$54.90	8.362%	$59.4907	$59.49	$59.50	$59.50
Purchase #2	$62.34	11.521%	$69.5222	$69.52	$69.50	$69.50
Purchase #3	$173.59	7.278%	$186.2239	$186.22	$186.20	$186.20
Purchase #4	$220.67	6.640%	$235.3225	$235.32	$235.30	$235.30
Purchase #5	$210.34	13.469%	$238.6707	$238.67	$238.65	$238.70
Purchase #6	$205.90	11.607%	$229.7988	$229.80	$229.80	$229.80
Purchase #7	$88.42	11.587%	$98.6652	$98.67	$98.65	$98.70
7 purchase totals =	$1,016.16		$1,117.6940	$1,117.69	$1,117.60	$1,117.70