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	$136.41	4.408%	$142.423	$142.42	$142.40	$142.40
Purchase #2	$194.66	13.867%	$221.6535	$221.65	$221.65	$221.70
Purchase #3	$53.33	11.230%	$59.319	$59.32	$59.30	$59.30
Purchase #4	$144.41	5.393%	$152.198	$152.20	$152.20	$152.20
Purchase #5	$101.89	5.378%	$107.3696	$107.37	$107.35	$107.40
Purchase #6	$99.26	5.179%	$104.4007	$104.40	$104.40	$104.40
Purchase #7	$104.36	5.393%	$109.9881	$109.99	$110.00	$110.00
7 purchase totals =	$834.32		$897.3519	$897.35	$897.30	$897.40