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	$123.25	7.565%	$132.5739	$132.57	$132.55	$132.60
Purchase #2	$235.68	13.347%	$267.1362	$267.14	$267.15	$267.10
Purchase #3	$149.56	4.471%	$156.2468	$156.25	$156.25	$156.20
Purchase #4	$247.55	6.454%	$263.5269	$263.53	$263.55	$263.50
Purchase #5	$69.85	3.465%	$72.2703	$72.27	$72.25	$72.30
Purchase #6	$147.45	5.401%	$155.4138	$155.41	$155.40	$155.40
Purchase #7	$144.72	13.798%	$164.6885	$164.69	$164.70	$164.70
7 purchase totals =	$1,118.06		$1,211.8564	$1,211.86	$1,211.85	$1,211.80