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	$162.93	3.250%	$168.2252	$168.23	$168.25	$168.20
Purchase #2	$169.83	13.351%	$192.504	$192.50	$192.50	$192.50
Purchase #3	$98.41	11.104%	$109.3374	$109.34	$109.35	$109.30
Purchase #4	$115.30	10.542%	$127.4549	$127.45	$127.45	$127.50
Purchase #5	$107.88	11.740%	$120.5451	$120.55	$120.55	$120.50
Purchase #6	$200.76	4.390%	$209.5734	$209.57	$209.55	$209.60
Purchase #7	$113.63	4.510%	$118.7547	$118.75	$118.75	$118.80
7 purchase totals =	$968.74		$1,046.3947	$1,046.39	$1,046.40	$1,046.40