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	$231.57	8.109%	$250.348	$250.35	$250.35	$250.30
Purchase #2	$249.72	9.506%	$273.4584	$273.46	$273.45	$273.50
Purchase #3	$96.92	12.605%	$109.1368	$109.14	$109.15	$109.10
Purchase #4	$249.51	8.501%	$270.7208	$270.72	$270.70	$270.70
Purchase #5	$59.27	6.138%	$62.908	$62.91	$62.90	$62.90
Purchase #6	$162.82	9.487%	$178.2667	$178.27	$178.25	$178.30
Purchase #7	$8.38	13.814%	$9.5376	$9.54	$9.55	$9.50
7 purchase totals =	$1,058.19		$1,154.3763	$1,154.39	$1,154.35	$1,154.30