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	$93.77	5.667%	$99.0839	$99.08	$99.10	$99.10
Purchase #2	$228.73	4.185%	$238.3024	$238.30	$238.30	$238.30
Purchase #3	$152.42	9.793%	$167.3465	$167.35	$167.35	$167.30
Purchase #4	$247.32	6.804%	$264.1477	$264.15	$264.15	$264.10
Purchase #5	$120.85	13.437%	$137.0886	$137.09	$137.10	$137.10
Purchase #6	$58.52	9.300%	$63.9624	$63.96	$63.95	$64.00
Purchase #7	$36.35	5.687%	$38.4172	$38.42	$38.40	$38.40
7 purchase totals =	$937.96		$1,008.3487	$1,008.35	$1,008.35	$1,008.30