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	$91.95	9.193%	$100.403	$100.40	$100.40	$100.40
Purchase #2	$245.62	8.728%	$267.0577	$267.06	$267.05	$267.10
Purchase #3	$58.56	11.744%	$65.4373	$65.44	$65.45	$65.40
Purchase #4	$127.47	7.364%	$136.8569	$136.86	$136.85	$136.90
Purchase #5	$193.76	8.131%	$209.5146	$209.51	$209.50	$209.50
Purchase #6	$161.51	4.451%	$168.6988	$168.70	$168.70	$168.70
Purchase #7	$94.69	11.345%	$105.4326	$105.43	$105.45	$105.40
7 purchase totals =	$973.56		$1,053.4009	$1,053.40	$1,053.40	$1,053.40