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	$226.62	4.372%	$236.5278	$236.53	$236.55	$236.50
Purchase #2	$94.43	7.500%	$101.5123	$101.51	$101.50	$101.50
Purchase #3	$141.36	5.649%	$149.3454	$149.35	$149.35	$149.30
Purchase #4	$101.63	3.433%	$105.119	$105.12	$105.10	$105.10
Purchase #5	$109.27	6.371%	$116.2316	$116.23	$116.25	$116.20
Purchase #6	$157.69	11.155%	$175.2803	$175.28	$175.30	$175.30
Purchase #7	$86.33	4.294%	$90.037	$90.04	$90.05	$90.00
7 purchase totals =	$917.33		$974.0534	$974.06	$974.10	$973.90