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	$158.66	6.839%	$169.5108	$169.51	$169.50	$169.50
Purchase #2	$245.90	6.233%	$261.2269	$261.23	$261.25	$261.20
Purchase #3	$147.35	12.356%	$165.5566	$165.56	$165.55	$165.60
Purchase #4	$73.39	6.645%	$78.2668	$78.27	$78.25	$78.30
Purchase #5	$196.41	8.641%	$213.3818	$213.38	$213.40	$213.40
Purchase #6	$184.32	6.818%	$196.8869	$196.89	$196.90	$196.90
Purchase #7	$57.69	8.530%	$62.611	$62.61	$62.60	$62.60
7 purchase totals =	$1,063.72		$1,147.4408	$1,147.45	$1,147.45	$1,147.50