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	$187.66	4.542%	$196.1835	$196.18	$196.20	$196.20
Purchase #2	$52.29	3.807%	$54.2807	$54.28	$54.30	$54.30
Purchase #3	$158.75	8.166%	$171.7135	$171.71	$171.70	$171.70
Purchase #4	$50.48	3.658%	$52.3266	$52.33	$52.35	$52.30
Purchase #5	$174.85	3.451%	$180.8841	$180.88	$180.90	$180.90
Purchase #6	$28.53	9.608%	$31.2712	$31.27	$31.25	$31.30
Purchase #7	$7.97	3.673%	$8.2627	$8.26	$8.25	$8.30
7 purchase totals =	$660.53		$694.9223	$694.91	$694.95	$695.00