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	$169.34	9.181%	$184.8871	$184.89	$184.90	$184.90
Purchase #2	$7.87	7.392%	$8.4518	$8.45	$8.45	$8.50
Purchase #3	$219.72	6.191%	$233.3229	$233.32	$233.30	$233.30
Purchase #4	$163.45	3.478%	$169.1348	$169.13	$169.15	$169.10
Purchase #5	$178.52	5.398%	$188.1565	$188.16	$188.15	$188.20
Purchase #6	$99.71	9.821%	$109.5025	$109.50	$109.50	$109.50
Purchase #7	$232.38	9.459%	$254.3608	$254.36	$254.35	$254.40
7 purchase totals =	$1,070.99		$1,147.8164	$1,147.81	$1,147.80	$1,147.90