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	$162.32	4.459%	$169.5578	$169.56	$169.55	$169.60
Purchase #2	$55.72	6.391%	$59.2811	$59.28	$59.30	$59.30
Purchase #3	$121.37	7.343%	$130.2822	$130.28	$130.30	$130.30
Purchase #4	$92.99	4.134%	$96.8342	$96.83	$96.85	$96.80
Purchase #5	$220.46	9.413%	$241.2119	$241.21	$241.20	$241.20
Purchase #6	$60.79	10.254%	$67.0234	$67.02	$67.00	$67.00
Purchase #7	$203.69	3.412%	$210.6399	$210.64	$210.65	$210.60
7 purchase totals =	$917.34		$974.8305	$974.82	$974.85	$974.80