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	$140.32	8.446%	$152.1714	$152.17	$152.15	$152.20
Purchase #2	$161.39	8.119%	$174.4933	$174.49	$174.50	$174.50
Purchase #3	$46.69	9.759%	$51.2465	$51.25	$51.25	$51.20
Purchase #4	$54.76	11.829%	$61.2376	$61.24	$61.25	$61.20
Purchase #5	$71.89	5.203%	$75.6304	$75.63	$75.65	$75.60
Purchase #6	$22.86	9.857%	$25.1133	$25.11	$25.10	$25.10
Purchase #7	$18.97	12.759%	$21.3904	$21.39	$21.40	$21.40
7 purchase totals =	$516.88		$561.2829	$561.28	$561.30	$561.20