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	$176.92	10.388%	$195.2984	$195.30	$195.30	$195.30
Purchase #2	$49.79	7.674%	$53.6109	$53.61	$53.60	$53.60
Purchase #3	$76.60	7.466%	$82.319	$82.32	$82.30	$82.30
Purchase #4	$129.68	3.490%	$134.2058	$134.21	$134.20	$134.20
Purchase #5	$181.80	4.320%	$189.6538	$189.65	$189.65	$189.70
Purchase #6	$73.46	11.702%	$82.0563	$82.06	$82.05	$82.10
Purchase #7	$53.71	10.340%	$59.2636	$59.26	$59.25	$59.30
7 purchase totals =	$741.96		$796.4078	$796.41	$796.35	$796.50