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	$141.27	4.428%	$147.5254	$147.53	$147.55	$147.50
Purchase #2	$49.70	11.564%	$55.4473	$55.45	$55.45	$55.40
Purchase #3	$138.56	11.324%	$154.2505	$154.25	$154.25	$154.30
Purchase #4	$172.40	7.614%	$185.5265	$185.53	$185.55	$185.50
Purchase #5	$79.30	9.170%	$86.5718	$86.57	$86.55	$86.60
Purchase #6	$234.39	12.595%	$263.9114	$263.91	$263.90	$263.90
Purchase #7	$226.76	11.106%	$251.944	$251.94	$251.95	$251.90
7 purchase totals =	$1,042.38		$1,145.1769	$1,145.18	$1,145.20	$1,145.10