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	$178.64	4.488%	$186.6574	$186.66	$186.65	$186.70
Purchase #2	$233.87	4.383%	$244.1205	$244.12	$244.10	$244.10
Purchase #3	$170.52	10.751%	$188.8526	$188.85	$188.85	$188.90
Purchase #4	$40.63	10.842%	$45.0351	$45.04	$45.05	$45.00
Purchase #5	$194.76	9.655%	$213.5641	$213.56	$213.55	$213.60
Purchase #6	$122.90	3.568%	$127.2851	$127.29	$127.30	$127.30
Purchase #7	$76.31	8.211%	$82.5758	$82.58	$82.60	$82.60
7 purchase totals =	$1,017.63		$1,088.0906	$1,088.10	$1,088.10	$1,088.20