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	$147.90	11.222%	$164.4973	$164.50	$164.50	$164.50
Purchase #2	$63.28	13.716%	$71.9595	$71.96	$71.95	$72.00
Purchase #3	$227.88	6.720%	$243.1935	$243.19	$243.20	$243.20
Purchase #4	$171.76	11.511%	$191.5313	$191.53	$191.55	$191.50
Purchase #5	$227.85	5.496%	$240.3726	$240.37	$240.35	$240.40
Purchase #6	$180.47	4.411%	$188.4305	$188.43	$188.45	$188.40
Purchase #7	$53.99	4.253%	$56.2862	$56.29	$56.30	$56.30
7 purchase totals =	$1,073.13		$1,156.2709	$1,156.27	$1,156.30	$1,156.30