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	$147.63	5.608%	$155.9091	$155.91	$155.90	$155.90
Purchase #2	$31.27	4.723%	$32.7469	$32.75	$32.75	$32.70
Purchase #3	$59.61	10.136%	$65.6521	$65.65	$65.65	$65.70
Purchase #4	$73.44	13.813%	$83.5843	$83.58	$83.60	$83.60
Purchase #5	$176.31	4.754%	$184.6918	$184.69	$184.70	$184.70
Purchase #6	$84.66	6.695%	$90.328	$90.33	$90.35	$90.30
Purchase #7	$170.76	7.562%	$183.6729	$183.67	$183.65	$183.70
7 purchase totals =	$743.68		$796.5851	$796.58	$796.60	$796.60