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	$144.77	5.478%	$152.7005	$152.70	$152.70	$152.70
Purchase #2	$171.84	5.428%	$181.1675	$181.17	$181.15	$181.20
Purchase #3	$79.97	11.761%	$89.3753	$89.38	$89.40	$89.40
Purchase #4	$197.26	5.150%	$207.4189	$207.42	$207.40	$207.40
Purchase #5	$218.72	5.546%	$230.8502	$230.85	$230.85	$230.90
Purchase #6	$168.42	12.158%	$188.8965	$188.90	$188.90	$188.90
Purchase #7	$184.52	3.392%	$190.7789	$190.78	$190.80	$190.80
7 purchase totals =	$1,165.50		$1,241.1878	$1,241.20	$1,241.20	$1,241.30