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	$160.31	6.687%	$171.0299	$171.03	$171.05	$171.00
Purchase #2	$103.49	5.766%	$109.4572	$109.46	$109.45	$109.50
Purchase #3	$57.36	8.114%	$62.0142	$62.01	$62.00	$62.00
Purchase #4	$195.59	13.528%	$222.0494	$222.05	$222.05	$222.00
Purchase #5	$93.42	8.836%	$101.6746	$101.67	$101.65	$101.70
Purchase #6	$147.27	13.670%	$167.4018	$167.40	$167.40	$167.40
Purchase #7	$248.29	8.792%	$270.1197	$270.12	$270.10	$270.10
7 purchase totals =	$1,005.73		$1,103.7468	$1,103.74	$1,103.70	$1,103.70