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	$59.63	5.169%	$62.7123	$62.71	$62.70	$62.70
Purchase #2	$160.51	6.731%	$171.3139	$171.31	$171.30	$171.30
Purchase #3	$161.38	3.789%	$167.4947	$167.49	$167.50	$167.50
Purchase #4	$87.69	9.616%	$96.1223	$96.12	$96.10	$96.10
Purchase #5	$6.88	4.113%	$7.163	$7.16	$7.15	$7.20
Purchase #6	$58.77	9.825%	$64.5442	$64.54	$64.55	$64.50
Purchase #7	$123.65	10.135%	$136.1819	$136.18	$136.20	$136.20
7 purchase totals =	$658.51		$705.5323	$705.51	$705.50	$705.50