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	$195.93	6.123%	$207.9268	$207.93	$207.95	$207.90
Purchase #2	$184.88	6.194%	$196.3315	$196.33	$196.35	$196.30
Purchase #3	$50.46	12.729%	$56.8831	$56.88	$56.90	$56.90
Purchase #4	$124.70	8.213%	$134.9416	$134.94	$134.95	$134.90
Purchase #5	$247.36	6.418%	$263.2356	$263.24	$263.25	$263.20
Purchase #6	$88.56	11.340%	$98.6027	$98.60	$98.60	$98.60
Purchase #7	$53.98	10.581%	$59.6916	$59.69	$59.70	$59.70
7 purchase totals =	$945.87		$1,017.6129	$1,017.61	$1,017.70	$1,017.50