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	$165.65	7.795%	$178.5624	$178.56	$178.55	$178.60
Purchase #2	$111.35	9.568%	$122.004	$122.00	$122.00	$122.00
Purchase #3	$81.83	9.412%	$89.5318	$89.53	$89.55	$89.50
Purchase #4	$50.35	4.696%	$52.7144	$52.71	$52.70	$52.70
Purchase #5	$230.46	10.784%	$255.3128	$255.31	$255.30	$255.30
Purchase #6	$174.70	3.637%	$181.0538	$181.05	$181.05	$181.10
Purchase #7	$158.38	4.616%	$165.6908	$165.69	$165.70	$165.70
7 purchase totals =	$972.72		$1,044.8700	$1,044.85	$1,044.85	$1,044.90