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	$186.46	5.391%	$196.5121	$196.51	$196.50	$196.50
Purchase #2	$219.53	13.357%	$248.8526	$248.85	$248.85	$248.90
Purchase #3	$148.88	6.790%	$158.989	$158.99	$159.00	$159.00
Purchase #4	$67.86	13.712%	$77.165	$77.17	$77.15	$77.20
Purchase #5	$73.36	4.253%	$76.48	$76.48	$76.50	$76.50
Purchase #6	$180.34	4.489%	$188.4355	$188.44	$188.45	$188.40
Purchase #7	$133.57	7.501%	$143.5891	$143.59	$143.60	$143.60
7 purchase totals =	$1,010.00		$1,090.0233	$1,090.03	$1,090.05	$1,090.10