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	$173.59	7.561%	$186.7151	$186.72	$186.70	$186.70
Purchase #2	$80.98	8.557%	$87.9095	$87.91	$87.90	$87.90
Purchase #3	$82.68	3.860%	$85.8714	$85.87	$85.85	$85.90
Purchase #4	$78.66	6.315%	$83.6274	$83.63	$83.65	$83.60
Purchase #5	$70.52	3.738%	$73.156	$73.16	$73.15	$73.20
Purchase #6	$105.34	6.666%	$112.362	$112.36	$112.35	$112.40
Purchase #7	$196.77	11.362%	$219.127	$219.13	$219.15	$219.10
7 purchase totals =	$788.54		$848.7684	$848.78	$848.75	$848.80