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	$163.71	6.272%	$173.9779	$173.98	$174.00	$174.00
Purchase #2	$20.26	7.629%	$21.8056	$21.81	$21.80	$21.80
Purchase #3	$179.79	8.850%	$195.7014	$195.70	$195.70	$195.70
Purchase #4	$234.76	10.429%	$259.2431	$259.24	$259.25	$259.20
Purchase #5	$109.70	12.442%	$123.3489	$123.35	$123.35	$123.30
Purchase #6	$85.98	4.394%	$89.758	$89.76	$89.75	$89.80
Purchase #7	$148.32	13.480%	$168.3135	$168.31	$168.30	$168.30
7 purchase totals =	$942.52		$1,032.1484	$1,032.15	$1,032.15	$1,032.10