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	$234.81	3.606%	$243.2772	$243.28	$243.30	$243.30
Purchase #2	$231.44	4.446%	$241.7298	$241.73	$241.75	$241.70
Purchase #3	$72.82	10.236%	$80.2739	$80.27	$80.25	$80.30
Purchase #4	$156.30	7.152%	$167.4786	$167.48	$167.50	$167.50
Purchase #5	$108.94	6.623%	$116.1551	$116.16	$116.15	$116.20
Purchase #6	$86.72	5.850%	$91.7931	$91.79	$91.80	$91.80
Purchase #7	$234.57	5.860%	$248.3158	$248.32	$248.30	$248.30
7 purchase totals =	$1,125.60		$1,189.0235	$1,189.03	$1,189.05	$1,189.10