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	$244.41	9.830%	$268.4355	$268.44	$268.45	$268.40
Purchase #2	$145.38	7.798%	$156.7167	$156.72	$156.70	$156.70
Purchase #3	$129.56	11.296%	$144.1951	$144.20	$144.20	$144.20
Purchase #4	$244.35	8.362%	$264.7825	$264.78	$264.80	$264.80
Purchase #5	$158.28	13.870%	$180.2334	$180.23	$180.25	$180.20
Purchase #6	$82.78	8.358%	$89.6988	$89.70	$89.70	$89.70
Purchase #7	$39.66	6.714%	$42.3228	$42.32	$42.30	$42.30
7 purchase totals =	$1,044.42		$1,146.3848	$1,146.39	$1,146.40	$1,146.30