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	$54.40	12.535%	$61.219	$61.22	$61.20	$61.20
Purchase #2	$48.41	11.671%	$54.0599	$54.06	$54.05	$54.10
Purchase #3	$70.26	13.712%	$79.8941	$79.89	$79.90	$79.90
Purchase #4	$6.62	12.119%	$7.4223	$7.42	$7.40	$7.40
Purchase #5	$233.87	3.161%	$241.2626	$241.26	$241.25	$241.30
Purchase #6	$200.73	11.411%	$223.6353	$223.64	$223.65	$223.60
Purchase #7	$127.92	13.524%	$145.2199	$145.22	$145.20	$145.20
7 purchase totals =	$742.21		$812.7131	$812.71	$812.65	$812.70